Networks

Networks

1. LAN

   • local area network
     • a network confined to one location or organisation
   • resources only available on that LAN

2. Wan

   • wide area network
     • a network of LANs spanning a wide area
   • internet is an example of a WAN

3. topologies

   • bus
     • a single cable connects all the computers
     • all the clients and servers connect to this cable
     • terminators are attached to each end of the cable
     • advantages
       • cheap
       • easy to install
       • no extra equipment required
     • disadvantages
       • high chance of collisions
       • more computers mean more collisions
       • only suitable for small networks
       • damage to the wire results in catastrophic failure
   • ring
     • each computer is connected to two other computers in a ring formation
     • each computer receives signals from one of it's connected computers
     • if the data is for itself, it reads it, if not it transmits it to the next computer
     • the data travels around the ring in one direction until it reaches its intended recipent
     • advantages
       • no collisions
       • number of computers does not affect speed
     • disadvantages
       • one faulty cable or computer results in full failure
       • more difficult to add new computers
   • star
     • all computers connected to central hub or switch
     • hub sends each message to all the other computers
     • a switch checks the address and sends it only to the correct computer
     • advantages
       • no collisions
       • failure of cable or computer is not catastrophic
       • easy to add new computers
     • disadvantages
       • expensive
       • failure of hub/switch results in full failure
   • mesh
     • circuit switching
     • packet switching
     • pathfinding
     • each computer is connected to one or more other computers
     • full mesh = every computer connected to every other computer
     • partial mesh = only some computers connected to others
     • advantages
       • zero catastrophic failure, always different path
       • multiple transmissions can happen simutaineously
     • disadvantages
       • redundancy- lot of unnecessary connections
       • expensive
       • difficult to maintain

4. advantages

   • allows computers to share files so they are accessible on all computers in network
   • ...share resources such as printers and internet
   • ...provide a single username and password that can be used on all computers

5. disadvantages

   • expensive, more hardware is needed
   • more room for error, if something goes wrong it can affect every compter
   • difficult, it requires a lot of technical expertise

6. protocols

   • standard
     • standard protocols are well known protocols that are widely used in a variety of applications
   • HTTP
     • ... is the standard protocol used for requesting an HTML file from a web server
   • HTTPS
     • ... is a secure version of HTTP which encrypts the data before sending it so that it can't be intercepted along the way
   • FTP
     • ...protocol for transferring files between two computers
     • commonly used by web developers for uploading their HTML files to their servers
   • POP3
     • ...protocol for downloading email from a mail server
   • SMTP
     • ...protocol for uploading email to a mail server